1. Field of the Invention
The present invention is directed to a novel resist composition capable of submicron lithographic patterns. In particular, the present invention is directed to a resist composition for positive tone images that has deep UV-light (200-300 nanometers) sensitivity and high resistance to oxygen reactive ion etching.
2. Description of the Prior Art
In the manufacture of various semiconductor devices wherein an oxide nitride or an organic polymer coating is formed on a semiconductor substrate, it is often required to remove selected portions of these coatings. This is done conventionally by applying a photoresist film to the desired substrate, imagewise exposing the photoresist to a source of radiation, such as ultra violet light, electron beam or x-rays, developing the exposed photoresist with a solvent to form a relief pattern which is replicated into the underlying inorganic or organic polymer layer by wet processing or dry etching according to conventional reactive ion etching techniques using oxygen or fluorocarbon gases as the etchant. In positive photoresists there is a significant increase in the solubility of the regions exposed to the radiation relative to the unexposed regions while in the case of negative photoresists the regions exposed to the radiation become relatively less soluble. After etching, the remaining photoresist is stripped from the substrate.
With regard to the methods of etching enumerates above, chemical etching, or wet etching has been eminently successful. However, with the continued miniaturization of semiconductor integrated circuits to achieve greater component density and smaller units of large scale integrated circuitry, the art is rapidly approaching a point where wet etching may become impractical for providing the high resolution required for fine definition of high density metallization network as the duration of the etching must be carefully controlled to prevent under or over-etching of the film layer.
Dry etching, and in particular oxygen reactive ion etching of organic polymer coatings as come to be recognized as a superior and practical alternative to wet etching, the etching equipment assuring adequate process control of the most precise thin film patterns.
One of the problems associated with reactive ion etching of thin films, however, is that most of the prior art positive photoresist compositions have high each rates under the conditions of reactive ion etching with etchant gases such as oxygen of the underlying layers and thus have limited application as an etch mask.
Attempts to improve the resistance of the photoresist to oxygen reactive ion etching generally reduce the sensitivity of the photoresist to radiation.